Collectors: Aggregation Operations

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

public class CollectorsDemo {

    public static void main(String args[]) {
        List<Employee> employeeList = new ArrayList<>();
        employeeList.add(new Employee("Alex", 23, 23000));
        employeeList.add(new Employee("Ben", 63, 25000));
        employeeList.add(new Employee("Dave", 34, 56000));
        employeeList.add(new Employee("Jodi", 43, 67000));
        employeeList.add(new Employee("Ryan", 53, 54000));

        long count = employeeList.stream()
                .filter(emp -> emp.getAge() > 30)
                .collect(Collectors.counting()); // Using the counting() method to get count of employees.

        System.out.println(count);
    }
}

class Employee {
    String name;
    int age;
    int salary;

    Employee(String name) {
        this.name = name;
    }

    Employee(String name, int age, int salary) {
        this.name = name;
        this.age = age;
        this.salary = salary;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    public int getSalary() {
        return salary;
    }

    @Override
    public String toString() {
        return "Employee{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", salary=" + salary +
                '}';
    }
}